1. Field of the Invention
This invention relates to a device for temporarily anesthetizing a living tissue by applying a pressure on the tissue, particularly in order to alleviate or reduce the sensation of pain associated with the subsequent puncturing of living tissue. In particular, it relates to a pressure anesthesia device useful in dental procedures.
2. Description of the Prior Art
It is well known that certain areas of the human body are more sensitive to pain than others. This is particularly true for the tissues of the oral cavity. Therefore, it is often necessary to anesthetize oral tissues prior to the initiation of dental procedures. To reduce the pain associated with the dental procedures, an anesthetic can be injected into the gum or palate by means of an injection needle. However, the injection itself, and particularly the puncture of the living gum or palate tissue is quite painful. It has therefore been desirable to reduce the pain associated with the insertion of an injection needle.
This goal can be attained by local cooling. Another approach, more often used and taught, is pressure anesthesia which is based on a long-known phenomenon of the puncture pain being partially masked by a lesser pain sensation influenced by pressing a solid object against the body area to be punctured. This phenomenon is particularly occuring in the oral areas.
A number of devices utilizing this pressure anesthesia effect have been proposed to date. For instance, U.S. Pat. No. 2,479,645 to Silverstein describes an instrument with an approximately spherical bead to be pressed against the tissue. The bead has a straight diametrical opening for a hypodermic needle to be passed there through, and a bottomless slot extending over the length of the opening to the part of the bead which comes into contact with the tissue to be punctured. The slot has a width less than the diameter of the opening. This enables the device to be withdrawn from the patient's mouth while the needle is still inserted.
U.S Pat. No. 4,681,101, issued Jul. 21, 1987, to Bicoll discloses a device with one or two disc-shaped bodies having each an aperture there through. The flat body is placed and pressed against the surface of the living tissue to anesthetize it and then an injection needle is passed through the aperture into the tissue.
The above mentioned devices do not address the problem of locating the opening or aperture in the pressure tip of the device with the hypodermic needle. The problem is easily appreciated when considering that, for example, the diameter of the Bicoll aperture is 1 mm. The task of inserting the needle into a small opening in the spherical bead of Silverstein appears to be quite difficult as well.
U.S. Pat. No. 2,044,410 issued Jun. 16, 1936 to Thornberry attempts to solve the problem. In the device disclosed therein, an upturned tongue at the end of a dental instrument, in the vicinity of a passage, serves to guide the needle toward the passage and to protect the tissue from inadvertent sticking.
Although the Thornberry device is useful, it has certain limitations in that it does not eliminate the possibility of unwanted sticking and is relatively bulky. In addition, it does not have a slot for the safe withdrawal of the device once the needle is inserted. Accordingly, there still is a need for a relatively safe and effective instrument for carrying out dental pressure anesthesia.